FR3020396A1 - METHOD FOR INSTALLING AND IMPLEMENTING A RIGID TUBE FROM A VESSEL OR FLOATING SUPPORT - Google Patents

Abstract

The present invention relates to a method for installing and implementing a rigid tube (10), called the main tube, in which the following steps are performed: a) one end of said main tube is lowered from a ship or floating support ( 13) at the surface (14) to below the sea level (14) for connection to submerged underwater equipment (16), preferably at the bottom of the sea (17), and b) maintaining the main tube thus immersed for a given period of time, characterized in that said main tube (10) is passed through a cylindrical orifice (4) with a circular section of a constraint limiting device, said orifice comprising an internal lining sliding (3) secured to a support structure (9) integral with said vessel or floating support, the service tube being thus able to slide in contact against said sliding coating during steps a) and b).

Description

The present invention relates to the field of submarine installation and the implementation of rigid pipes or pipes made of steel, from a ship or floating support in the form of a pipe or a pipe. surface to immersed equipment, preferably to the bottom of the sea. These rigid tubes may be tubes called service tubes used to test or ensure the maintenance from the sea surface of said subsea equipment, or conduits for transporting production or service fluids to such equipment, in particular submarine pipelines for transporting petroleum or associated fluids, or wellheads or other equipment. These rigid tubes are more particularly intended to test said underwater equipment from the surface by conveying liquid or gaseous products thereto at variable temperatures and pressures. In particular, the tests carried out consist in filling the underwater pipe for the production of a liquid for cleaning the line, such as seawater treated under pressure and, for example, passing a scraper there for clean. The underwater pipe can then be dried by sending a gas such as air. The production line can also be subjected to a process of inerting with monoethanol glycol and / or nitrogen. The service tubes are rigid steel or metal tubes, or other materials, in particular composite, wound on a coil on the surface and then deployed in immersion in the sea, to be connected to the submerged equipment or the bottom of the sea, then operate a said test or said maintenance by sending said liquids or gases, and finally recovered from the floating support or ship by winding. These rollable service tubes are also known under the name "COILED TUBING" which are uncoiled and rewound several times. In general, their upper end remains wound partly on the coil and is not completely unrolled. However, in some cases, the upper end of the tube may be fully unwound and fixed on the surface.

In practice, these service tubes have relatively small diameter diameters compared to the diameters of the standard subsea oil production lines, especially steel service tubes with diameters of less than 10 ", and more particularly 1.5" to 6 ", more particularly between 1.75" and 4.5 ", more particularly from 50 to 100mm for interventions over 1000m or even 2000m deep.These rigid steel service tubes are mechanically plasticized of the term during their winding, that is to say that the stresses that are applied to the tube go beyond the elastic limit of the tube and that it is permanently deformed. tube, the tension that is applied on it to unroll it makes it possible to straighten it at the output of the coil, possibly in combination with a straightener The rigid steel service tubes of the type concerned present more particularly elastic limits of 335 MPa to 750MPa. Rigid service tubes of this type are described in the state of the art, in particular in WO 2012/051335. Due to the successive windings and windings on the one hand, and on the other hand movements of the service tube during its deployments and operations, the service tube undergoes significant localized stress forces at its point of suspension on the surface . Thus the rolls, pitch and heave of the vessel or floating support and the action of waves, wind and / or currents on the service tube and the vessel or floating support induce high bending forces at the point of suspension and / or fixing the tube on the vessel or floating support, and this especially when the length and therefore the weight and the pressure of the fluids conveyed in the service tube are important.

To overcome this problem, the practical solution implemented to date consists in unrolling additional lengths of tubes regularly, in particular a few meters, so as to move the area of the service tube where the constraints. This solution is, however, applicable only for service tubes of small diameter, in particular less than 50 mm and for operation times of the service tube less than the day, which can be used for interventions with a depth of immersion limited to less than 1000m. Beyond this period, for interventions over 2000m in particular, and for larger diameter tubes the rigid tube is too tired and may break. More particularly, currently operating times are a few hours and the rigid line can be unrolled a few meters after each operation to minimize the fatigue that occurs in the same area of the rigid tube, while the durations of operations largely depth exceed the day or even the month and the risks of breaks in fatigue of the tube are very important with the disastrous consequences on equipment, personnel and equipment at the bottom of the sea in case of accident of rupture of tube. This solution is not applicable for applications at great depths where the service tube service life is in weeks and the required diameters are greater than 50 MM. Another problem encountered is the connection of the rigid tube termination to test equipment or equipment to be tested or operated. The rigid metal tube must have at its end a connecting element, particularly of the automatic connector type, of larger diameter than the service tube, to allow the connection of its end to a semi-rigid pipe or intermediate pipe most often. However, it is not easy to assemble such a connection element to the tube once its end is submerged at the bottom of the sea. The known solution to date consists in assembling at the surface of said connection element to the end of the service tube before its deployment at the bottom of the sea. Known stiffening devices ("bend stiffener") or bend restrictors applied to the ends of flexible pipes, as described in EP 2 503 093, FR 2 952 118, FR 2 871 511. The stiffeners or limiters of bends of flexible pipes are generally made in the form of conical parts made of synthetic materials, in particular elastomeric material of polyurethane type. Steel pieces of this type are also known applied to the rigid steel pipe end of the riser type in order to achieve the embedment by an inertial transition piece of the type called "joint tap" or "adapt joint" as described in WO 200913861. These parts are in extension of the existing pipe, generally welded to the pipe or flanged. The conical shape allows a transition of inertia by progressive and continuous decrease in diameter, starting from the most mechanically stressed point. Because these conical parts are integral with the end of the pipe, the forces supported by said pipe end are transferred to the conical part whose increase in section allows a greater distribution of the overall stress and a transition in softer stiffness and therefore a decrease in local constraints. The section of the conical piece gradually decreases as a function of the decrease in said stress, the latter being maximum at the point of connection or suspension of the pipe at its end. Solutions of this type applied to a tube as described above are not appropriate given the need to allow unwrapping and windings at the point of suspension of the upper end of the rigid tube surface. The object of the present invention is to provide a solution to the stress forces of the rigid tubes described above deployed from the surface to a great depth, more particularly to limit the dynamic fatigue in said rigid tube which results from its use in suspension from a ship or floating support surface during periods of significant operations, and thus increase the fatigue life of the rigid tube.

Another purpose is to facilitate the deployment of said rigid tube, especially for service tubes, from the surface. To do this, the present invention provides a method of implementing a rigid tube, hereinafter referred to as the main tube, preferably a main steel tube, from a floating vessel or support surface to below the level of the sea, preferably to be connected to underwater equipment preferably immersed to the bottom of the sea, in which the following steps are carried out: a) one end of said main tube is lowered from a ship or floating support in surface to below the sea level to be connected to underwater submerged equipment, preferably at the bottom of the sea, and b) maintaining said main tube thus immersed for a given period of time, characterized in that said main tube is passed through a cylindrical orifice with a circular cross section, of vertical axis (ZZ ') of a constraint limiting device called a sliding stiffener, said orifice called the first orifice comprising having a sliding inner liner in contact with said main tube, said sliding stiffener being integral with a support structure integral with said floating vessel or support extending outside said vessel or support floating above the sea surface an upper part of said main tube being held in suspension above said sliding stiffener, said main tube being thus able to slide in contact against said sliding coating during steps a) and b). More particularly, in step a), the following steps are performed: a.1) unwinding said main tube wound on a winding support on said vessel or said floating support, and a.2) lowering said main tube below sea level, preferably to said submerged underwater equipment, by sliding it through said sliding stiffener.

It is understood that said first orifice is substantially of the same diameter as said main tube with minimal mechanical clearance allowing its introduction and sliding in said orifice, for example 1 to 5 mmm depending on the diameters and length of the service tube. The game, although necessary for the introduction of said main tube into the stiffener must be kept to a minimum to ensure the effectiveness of said stiffener. It is understood that the vertical or slightly inclined axial direction of less than 300, more generally less than 100, of said cylindrical orifice of the stiffener means a direction perpendicular to a theoretical horizontal surface of the sea surface when the sea is and the vessel or floating support stationary or slightly inclined by less than 30 ° with respect to said perpendicular, more generally less than 100.

It is also understood that the main tube is slid for its use at the bottom of the sea from the ship or floating support, but also that said main tube remains slidable in the stiffener during its implementation in operation when the ship or floating support and said main tube are agitated movements related to wave swell, marine current and / or wind. The function of the sliding stiffener according to the invention is to transfer towards said support structure the bending forces undergone by said main tube in contact with the stiffener in the event of relative movements of the stiffener and said main tube, that is to say of transfer the bending moments undergone by said main tube due to its horizontal lateral movement and its curvature since the possible tensile and compressive forces are not taken up by the stiffener because of its sliding character. The application of this stiffener is therefore limited to the recovery of bend stiffener efforts.

This sliding anti-abrasive coating with a minimum of play prevents the deterioration of the service tube during its deployment and its use, the contact thereof with its guide point and surface suspension can undergo, in the absence slippery coating, a wear as harmful as the effect of a hacksaw on the tube due to multiple repeated sliding. The stiffening method and device according to the invention thus makes it possible to deploy a said main tube through said stiffener from a vessel or floating support surface to a great depth by minimizing the abrasion of said main tube during the ascents and descents of said tube and by limiting the dynamic fatigue in said main tube resulting from its use in suspension from the ship or floating support during important periods at sea, in practice the method and device according to the present invention makes it possible to multiply the fatigue life of said main tube by a safety factor often greater than 10. This invention also makes it possible to use the said main tube in larger sea states, thus limiting the expectation of an acceptable weather window. More particularly, the dimensions of the stiffener are defined so that the stress of said main tube does not exceed 50% to 80% of the elastic limit of the steel of the main tube. In practice, and by way of illustration, for usual main tubes with diameters of 1.5 to 8 "(not more than 100 mm) with an elastic limit of 350 to 750 MPa, immersed at a depth of 1000 to 3000 m, the stiffener will have a length L1 from 1 to 8 m and a maximum outer diameter of the current portion D1 from 100 to 200 mm for a half angle at the top of the cone from 0 to 50.

Because the stiffener takes up only the bending forces, that is dimensioned according to the maximum curvatures of the service tube and not its voltage and thus immersion depth. Indeed, although the expansion of said main tube can also be done in the radial direction (due to the pressure and temperature of the fluid conveyed), this radial expansion can never exceed 0.2% which is negligible, for example 0.2mm for a diameter of 100mm therefore lower than the game. In addition, note that the introduction of said main tube in the stiffener is without pressure at room temperature and therefore without expansion with the maximum play. Then, the radial expansion in operation will tend to decrease the game and increase the quality of the recovery function. More particularly, said sliding stiffener comprises a rigid solid part, preferably made of steel, traversed in its mass by a said cylindrical orifice, called the first orifice, of vertical axis (ZZ '), said rigid part comprising a running part having a surface external of revolution relative to the axis of said first cylindrical orifice preferably decreasing gradually and continuously from top to bottom of said stiffener to the lower end of said stiffener. Thus the increase in the stiffener section takes the forces and stresses experienced by said main tube and transferred to the stiffener at the maximum where the stress is highest at the upper level, that is to say at the point of connection or contact stiffener with support structure. More particularly, said current portion of the rigid piece constituting said stiffener has a frustoconical outer surface extending from and below an upper portion of said rigid piece defining a fastening flange around the upper end of said first orifice. In a preferred embodiment, said fixing flange forms a fixing plate fixed to or coming from a material with the upper end of said running part, said fixing plate resting and being fixed on a horizontal platform of said support structure, said mounting plate extending on a flat surface above said platform of larger size (D2) than that of the larger section (D1) of said running portion, preferably a said platinum plane surface with a coaxial circular circumference of that of said first orifice, preferably a platinum plane surface of larger size (D2) at least double, preferably at least 5 times, of that of said larger section (D1) of said conical part. When said flange or mounting plate is attached to the upper end of the running portion of the conical part, it is preferably fixed by welding or bolting. When it comes from material with the current part, it can be made by molding and / or forging in the form of the same forged piece of steel or by machining a forged part if necessary.

The main tube, the stiffener and the connecting tube may be any other rigid material such as composite materials. The increase in size, in particular a discontinuous increase in diameter at the level of the fastening flange relative to the current portion of the stiffener, makes it possible to increase the distribution area of the stress transferred onto the platform of the support structure and thus to reduce the constrained locally on the platform transferred from the upper end of the stiffener, that is to say where it is maximum. Thus, in practice, said mounting plate may have a reduced thickness relative to the maximum thickness of the current portion of the rigid part and may be fixed on the platform by bolts because the stress is greatly reduced. It will be understood that: the running portion passes through said platform and extends from and below said fixing plate and below said platform, its lower end being able to be submerged in the sea; and the section of current portion is a cross section, that is to say in a plane perpendicular to its vertical longitudinal axial direction.

More particularly still, said first orifice of said rigid stiffening member is covered on its surface in contact with said main tube with a sliding coating made of a low-friction anti-abrasion material chosen from a liquid material such as an oil, a viscous material such as a grease or a solid material such as a liner type plastic film layer coating, preferably made of thermoplastic material of the PE, PP, PA, PVDF or elastomer type, said plastic coating being furthermore preferably coating on its contact surface with said main tube (10) a low abrasion anti-abrasion material selected from a liquid material such as an oil, or a viscous material such as a grease.

More particularly, said main tube is coated with a low abrasion anti-abrasion material chosen from a liquid material such as an oil or a viscous material such as a grease, the treatment for producing this coating being preferably carried out after step a) and before introducing it into said first orifice.

The type of thermoplastic of the liner is defined according to the temperature of use. In most cases, HDPE is sufficient. But, above 60 ° C, we can use preferably the PP. This sliding abrasion-resistant coating with a minimum clearance prevents the deterioration of said main tube during its deployment and its use, the contact thereof with its guide point and surface suspension can undergo wear as harmful as a hacksaw on said tube in the absence of a sliding coating. It will also be noted that the clearance between said main tube and the first orifice increases as the said main tube deploys. The game will be reduced to a minimum. That is why, advantageously, the introduction of said tube into the stiffener requires grease to ensure good sliding. A grease box in which penetrates and slides said main tube, is then positioned above the stiffener to serve as a permanent lubricant during the deployment and the lift of said main tube. Of construction, said tubes are tubes with smooth surface and without burr, however a deburring collar may furthermore advantageously be mounted above the stiffener to eliminate or crush micro-defects that may risk damage to the liner . This is for example a small cylindrical block with a cutting edge in one or two parts into which penetrates and slides said main tube. This collar can be judiciously combined with the grease box. According to another particular advantageous feature, for the course of step a) said main tube is passed through a tensioning device and curvature reduction curvature associated with the winding and then in a grease box and a deburring collar, before its introduction into the stiffener, so that the outer surface of said tube is coated with grease before sliding in said first orifice. It is understood that this feature improves the sliding properties of said main tube within said first orifice. More particularly, a control test and / or the maintenance of an underwater pipe and / or a wellbore at the bottom of the sea is carried out by sending a liquid or a gas using said main pipe. whose lower end is connected to said underwater pipe and / or a wellbore at the bottom of the sea, preferably via a flexible or semi-rigid pipe. In a preferred embodiment, said stiffener is pre-equipped with a tube portion called a connecting tube fixed and / or reversibly suspended to said support structure and / or said stiffener, said connecting tube preferably being same diameter and preferably of identical composition to said main tube, said connecting tube being engaged in said first orifice and comprising at its lower end, below said stiffener, a connection element connected or able to be connected to a device, preferably a flexible or semi-rigid pipe, and before step a), the steps are carried out in which: - the end of said main pipe is connected to the upper end of said connecting pipe, preferably by welding and abrasion of the bead; welding, and - said connecting tube is detached from said stiffening device, and - it starts e by lowering said connecting tube. More particularly, said connecting tube comprises a removable clamp around a portion of said connecting tube protruding above said first port.

It is therefore understood that said connecting tube is substantially of the same diameter as said main tube and is of a length greater than that of said stiffener, more precisely greater than the length of said first orifice to allow its connections above and below said stiffener. Said connecting tube has several functions: - it serves to connect in particular the main tube by welding, welding, including the connection, being made on said support structure above the surface of the sea, in a dry zone, and therefore easy access, this connection being made on the surface it can be repaired or redone at will by re-winding of the main tube, provided however that this connection, including this welding being in operation at the bottom of the water is not subject to the elastic fatigue experienced by the main tube at its point of suspension on the surface, and - it is equipped at its lower end with a connection element itself previously welded on this connecting tube because it can not pass through said first orifice of the stiffening element for reasons of dimensions and tolerance, and said connection tube can then be connected to the underwater equipment intended to be mounted at the end of the main tube such as mooring or flexible or semi-rigid pipes or other equipment.

This embodiment is particularly advantageous in that it facilitates the connection of the end of said main tube to equipment intended to be immersed, in particular a flexible pipe intended to be connected to the end of said main tube via said connecting element. pre-equipped at the lower end of said connecting tube. More particularly, the upper end of the connecting tube protruding above the stiffener may end with a welding chamfer.

The entire stiffener and connecting tube can be easily manipulated and installed on said support structure on the ship or floating support before being assembled, in particular by welding, at the end of said main tube, said main tube can then be deployed equipped with its terminal connecting element of larger diameter than said first orifice of the stiffener. Failing this, said connecting element which is larger in diameter than the first orifice can not pass therethrough and must be mounted at the end of the service tube after deployment and sliding of that inside said first orifice. orifice which complicates the procedure of implementation of the main tube. During the final ascent of the main tube and its rewinding, its end including the stiffener and the connecting tube can be cut and said stiffener assembly and said connecting tube can be stored until a new use.

In total, the system according to the present invention is easy to use. Its theoretical life can be several years and in any case compatible with the life of the main tube. Thus, more particularly, it ensures the maintenance and stabilization of a rigid steel main tube unrolled from a vessel or floating support surface to the seabed and passing through a said stiffener after said descent and implemented, during a period of at least 24 hours, preferably at least 1 month without going up to the surface and / or unwinding an additional length. The present invention also provides an installation useful for the implementation of a method according to the invention characterized in that it comprises a support structure integral with a floating vessel or support surface, on which is fixed a stiffener comprising a rigid piece full of external surface of diameter revolution decreasing progressively and continuously from bottom to top of said stiffener to the lower end of said stiffener, preferably made of steel, comprising an axial orifice called first orifice comprising a sliding internal lining adapted to allow the sliding of a said main tube introduced into said first orifice in contact with said main tube. More particularly, said first orifice of said rigid stiffening member is covered on its surface in contact with the main tube with a sliding coating made of a low abrasion anti-abrasion material chosen from a liquid material such as an oil, a viscous material such as a grease or a solid material such as a liner-type plastic film layer coating, preferably made of thermoplastic material of the PE, PP, PA or PVDF type or an elastomer. More particularly, said stiffener is equipped with a portion of tube called connection tube reversibly fixed to said stiffener, said connecting tube being of the same diameter and preferably of identical composition to said main tube, said connecting tube being engaged in said first orifice and comprising at its lower end, below said stiffener, a connecting element connected or adapted to be connected to a equipment, preferably a flexible pipe. More particularly, said connecting tube comprises a removable clamp around a portion of said connecting tube protruding above said first port.

Other features and advantages of the present invention will emerge in the light of the following detailed description given with reference to the figures in which: FIGS. 1A to 1C are side views (FIG. 1A) and axial vertical section (FIG. 1B); and 1C) a sliding stiffener 1) according to the present invention pre-equipped with a connecting tube 5 (Figure 1B) and without connection tube (Figure 1C), and - Figure 2 shows a view of an installation connecting bottom / surface equipped with a stiffening device hereinafter called sliding stiffener according to the present invention. - Figure 3 shows the part of the installation at the ship, and - Figure 3A shows a detail at the junction of the sliding stiffener 1 on a structure or support beam 9 of the ship.

The sliding stiffener 1 as represented in the figures consists of a solid piece of rigid solid material such as steel optionally reinforced with glass or synthetic fibers comprising the following two parts: a conical running portion 2a and a platinum upper attachment 2b. The lower running portion 2a with an outer surface of frustoconical revolution extends over a length L1. It is perforated by a said first cylindrical orifice 4 with a circular section of the same axis ZZ 'as said frustoconical outer surface and passing through it from one side to the other. The diameter of the frustoconical outer surface of the running portion 2a varies from a maximum value D1 at its upper end to a minimum value d1 at its lower end. For the figures, the conical part has been represented with a linear generator and the diameters vary linearly. However, in another embodiment, the generatrix of the surface of revolution of the current portion 2a may be a parabola but in all cases the variation of the diameter will be progressive and continuous between the maximum value D1 and its minimum value d1.

The frustoconical running portion 2a is surmounted by a perforated plate forming a coaxial annular piece 2b perforated by the upper end of said first cylindrical orifice. The annular upper plate 2b has a cylindrical shape of larger diameter D2 greater than D1 and of thickness el. The larger diameter D2 of the annular plate 2b allows the underside 2b1 thereof to rest and is fixed by bolting and / or welding over the upper face of a platform of a support structure 9 secured to the ship or floating support described hereinafter with reference to FIG. 2.

In one embodiment, the current portion 2a of frustoconical outer surface can be made by machining from a tubular perforated piece with cylindrical outer surface with circular section, said machining making it possible to progressively reduce the thickness and thus the diameter. externally continuously along its length.

The part 2 can also and preferably be made in the form of a forged piece whose upper plate 2b is made of material with the lower running part 2a, said part 2 being continuously traversed by said first axial cylindrical orifice 4. In another embodiment embodiment, the annular upper plate 2b is welded to the upper end of the frustoconical surface portion 2a. The piece 2 comprises a sliding coating 3 in the form of an inner liner made of plastic material, preferably of thermoplastic material, of said first orifice called "liner". Such a liner can be made by "swagelining" as described in FR 2 876 773. To do this, the following steps are carried out: a) Preparation of a liner pipe 3-1 flexible thermoplastic material and elastic to the inside said first orifice, said lining pipe having a diameter slightly greater than the diameter of said first orifice. b) Heating said lining pipe by passing it in a heating furnace and then in a die to exit towards said first orifice with an outer diameter slightly smaller than the inner diameter of said first orifice. c) A first end of the liner pipe is introduced at a first end of said first port. Said first end of the lining pipe is equipped with a traction head connected to a winch outside said first orifice on the side of its second end. d) Pulling the lining pipe from the second end of the orifice 4. During this traction, the lining pipe thus sees its diameter reduce but also its nominal length increase. In a draw preparation phase, the inner wall of said first orifice is glued, for example with an epoxy type glue or a two component polyurethane glue. e) After pulling said lining pipe inside said first orifice to its second end, the traction is released on the liner pipe once it has passed through the entire first orifice. And, since it initially had a diameter greater than the diameter of the first orifice, said relaxed lining pipe is pressed and melt adhered due to its heating against the inner steel surface of the first orifice, the adhesion possibly being reinforced by gluing. Advantageously, the fastening flange 2b is coated on its upper surface with a portion 3b of the inner liner in continuity with the cylindrical lining 3a inside said first orifice 4. This upper flat part 3b ensures the protection of the upper face of the fixing flange 2b. In another embodiment, the thermoplastic inner liner is applied against the inner surface of said first hole by hooping. For the installation of a steel service pipe 3.5 "(89 mm) in diameter and a yield strength of 555 MPa intended to be deployed over a length of more than 2 km to be installed at approximately 2000 m of depth A sliding stiffener having the following dimensional characteristics will be used: - Li = 2 to 7 m, - e, thickness of the steel cone of the stiffener varies from: - e max = 10 to 50 mm at the top, to - e min = 2 to 3 mm at the bottom - thickness of the polyethylene (PE) coating = 5 to 25 mm, the flange 2b, reported by welding at the top of the stiffener 2a has a thickness el greater than the maximum thickness e max of In FIGS. 1A and 1B, the sliding stiffener 1 is equipped with a connection tube 5 of the same diameter and thickness as the service tube to which it is intended to be connected to its chamfered upper end 5a. lower is equipped with a male element e or female connector 6-1 again by shrinking or welding. The largest outer diameter D3 of said connecting member 6-1 is greater than the inner diameter of said first orifice d2. The upper end 5a of the connecting tube 5 extends above the upper fixing plate 2b. In one embodiment, the connecting tube 5 is thus kept in suspension with its upper end 5a extending above the plate 2b by means of a clamping clamp 7 enclosing the outer surface of the connecting tube. and resting over the upper face of the plate 2b. The external diameter of the connecting tube d3 in its running part offers a minimum clearance with the inner diameter d2 of the first orifice coated with said inner liner 3 so as to allow the tube 5 to slide through its upper end 5a introduced at the lower end of the first port of the conical part 2. In Figures 2 and 3, there is shown a complete bottom / surface connection installation showing the deployment of a rigid steel service tube 10 wound on a coil 12 on the bridge of a vessel or floating support 13. The steel service pipe 10 is unwound and passes through a straightening device 11 and then through a lubricating device and smoothing its outer surface 18. Then, its end is welded to the upper end 5a connecting tube 5 secured to a sliding stiffener 1 whose upper annular plate 2b is fixed on the upper face 9a of a platform of a supple structure ort 9, the frustoconical running portion 2a of the sliding stiffener passing through an orifice 8 of the platform 9 (FIG. 1C). Then, the connecting tube 5 is separated from the stiffener 1 so as to allow the sliding and deployment of the connecting tube 5 with the immersion service tube to the bottom sea. To do this, it disengages the clamp or collar 7 which held the connecting tube suspended in the sliding stiffener as shown in Figure 1A. In Figure 2, there is shown the service tube after unwinding and immersion of the end of the steel service tube equipped with its connecting tube. In FIG. 2, the connection element 6-1 at the end of the connection tube 5 is connected to an automatic connector complementary connection element 6 at the end of a flexible pipe 15, the other end of which allows access and maintain and / or perform tests on underwater equipment 16 resting at the bottom of the sea 18, such as a wellhead or underwater conduct of oil production. The connection of the equipment 15 to the lower end of the connection tube 5 can be performed before or after the uncoupling and immersion of the connection tube 5 with respect to the stiffener using a submarine robot of the type ROV.

Claims (15)

REVENDICATIONS1. A method of installing and implementing a rigid tube (10), called the main tube, preferably a main steel tube (10), wherein the following steps are carried out: a) one end of said main tube is lowered from a vessel or floating support (13) at the surface (14) to below sea level (14) to be connected to submerged underwater equipment (16), preferably at the bottom of the sea (17), and b) maintaining the main tube thus immersed for a given period of time, characterized in that said main tube (10) is passed through a cylindrical orifice (4) of circular section, preferably of vertical axis (ZZ '), a constraint limiting device called sliding stiffener (1), said orifice called first orifice comprising a sliding inner liner (3), said sliding stiffener (1) being integral with a support structure (9) solidaire said vessel or floating support extending to the outside ur of said vessel or support floating above the sea surface, an upper portion (10a) of said main tube being held in suspension above said sliding stiffener, the service tube being thus able to slide in contact against said coating sliding during steps a) and b). 2. Method according to claim 1, characterized in that said sliding stiffener (1) comprises a rigid solid part (2), preferably steel, traversed in its mass by a said cylindrical orifice (3) called first orifice, d ' vertical axis (ZZ '), said rigid part comprising a running part (2a) having an external surface of revolution with respect to the axis of said first cylindrical orifice (4), preferably diameter decreasing progressively and continuously from top to bottom said stiffener to the lower end of said stiffener. 3. Method according to claim 2, characterized in that said running portion (2a) of the rigid part constituting said sliding stiffener (1) has an outer surface of frustoconical shape extending from and below an upper portion (2b) of said rigid piece defining a fastening flange around the upper end of said first orifice (3). 4. Method according to claim 3, characterized in that said fixing flange (2b) forms a fixing plate fixed to or coming from a material with the upper end of said running part (2a), said fixing plate resting and being fixed on a horizontal platform of said support structure (9), said fixing plate (2b) extending on a flat surface above said platform of larger size (D3) than that of the larger section (D2) of said current portion, preferably a circular plane circular platinum surface coaxial with that of said first orifice, preferably a platinum plane surface at least double, preferably at least 5 times, that of said larger section ( D2) of said conical part (2a). 5. Method according to one of claims 1 to 4, characterized in that said first orifice (4) of said rigid stiffening member is covered on its surface in contact with said main tube of a sliding coating (3) consisting of a low abrasion anti-abrasion material selected from a liquid material such as an oil, a viscous material such as a grease or a solid material such as a liner type plastic film coating, preferably, thermoplastic material of the PE, PP, PA, PVDF or elastomer type, said plastic coating being furthermore preferably coated on its contact surface with said main tube (10) with a low-friction anti-abrasion material chosen from a material liquid such as an oil, or a viscous material such as a grease. 6. Method according to one of claims 1 to 5, characterized in that said main tube (10) is coated with a low abrasion anti-abrasion material selected from a liquid material such as an oil or a viscous material such as a grease, the production treatment of this coating being preferably carried out after step a) and before introducing it into said first orifice. 5 7. Method according to one of claims 1 to 6, characterized in that said sliding stiffener (1) is pre equipped with a tube portion called connecting tube (5) fixed and / or reversibly suspended from said structure support and / or said sliding stiffener, said connecting tube being preferably of the same diameter and preferably of identical composition to said main tube, said connecting tube being engaged in said first orifice (4) and comprising at its lower end below said stiffener, a connecting element (6-1) connected or adapted to be connected to a device (16), preferably a flexible or semi-rigid pipe, and before step a), the steps are carried out in which the end of the said main tube is connected to the upper end of the said connecting tube, preferably by welding and abrasion of the solder bead, and the said tube is separated from connection relative to said stiffening device, and - first descends said connecting tube. The method of claim 7, characterized in that said connecting tube comprises a removable clamp (7) around a portion of said connecting tube protruding above said first port. 9. Method according to one of claims 1 to 8, characterized in that step a), the following steps are carried out: a.1) unwinding said main tube wound on a winding support on said vessel or said floating support, and preferably the service tube is passed through a device (18) for tensioning and curvature reduction of curvature associated with the winding and then in a grease box and a deburring collar (18a), before it is introduced into the sliding stiffener (1), and a.2) said main tube is lowered to below sea level, preferably to a so-called submerged underwater equipment, by sliding it through said sliding stiffener. 10. Method according to one of claims 1 to 9, characterized in that in step b), it ensures the maintenance and stabilization of a said main steel tube (10) unrolled from a ship or floating support ( 13) at the surface (14) to the bottom of the sea (17) and passing through said sliding stiffener (1) after said descent and implementation, for a period of at least 24 hours, preferably at least 1 month without surfacing and / or unwinding an additional length. 11. Method according to one of claims 1 to 10, characterized in that a control test and / or maintenance of an underwater pipe and / or a wellbore (16) is carried out. seabed (17) by sending a liquid or a gas by means of said main tube whose lower end is connected to said underwater pipe and / or a wellbore (16) at the bottom of the sea, preferably via a flexible or semi-rigid pipe (15). 12. Installation useful for the implementation of a method according to one of claims 1 to 11, characterized in that it comprises a support structure (9) integral with a ship or floating support (13) on the surface ( 14), on which is fixed a sliding stiffener (1) comprising a rigid solid part (2) of external surface of diameter revolution decreasing progressively and continuously from top to bottom of said stiffener to the lower end of said stiffener, preferably made of steel, comprising an axial orifice called first orifice (4) comprising a sliding inner lining (3) capable of allowing the sliding of a said main tube introduced into said first orifice in contact with said main tube. 13. Installation according to claim 12, characterized in that said first orifice (4) of said rigid stiffening member is covered on its surface in contact with said main tube with a sliding coating (3) consisting of an anti-corrosive material. low-friction abrasion chosen from a liquid material such as an oil, a viscous material such as a grease or a solid material such as a liner-type plastic film layer coating, preferably made of a PE-type thermoplastic material , PP, PA, PVDF or an elastomer 14. Installation according to claim 12 or 13, characterized in that said sliding stiffener (1) is equipped with a tube portion called connecting tube (5) reversibly fixed to said stiffener, said connecting tube being likewise diameter and preference of composition identical to said main tube, said connecting tube being engaged in said first orifice (4) and comprising at its lower end, below said stiffener, a connecting element (6-1) connected or able to be connected an equipment (16), preferably a flexible or semi-rigid conduit (15). 15. Installation according to claim 14, characterized in that said connecting tube comprises a removable clamping collar (7) around a portion of said connecting tube projecting above said first orifice.